[MIPS] IP22: Fix warning.

  CC      arch/mips/sgi-ip22/ip22-berr.o
arch/mips/sgi-ip22/ip22-berr.c: In function 'ip22_be_interrupt':
arch/mips/sgi-ip22/ip22-berr.c:100: warning: passing argument 2 of 'die_if_kernel' discards qualifiers from pointer target type

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>